A　liquid　level　controller　for　steam-liquid　two　phase　flow　is　designed　based　on　the　fluid　dynamics　and　physical　properties　of　steam-liquid　two　phase　flow.　In　this　paper,　equations　are　provided　for　the　dimensions　design　of　the　main　parts　of　the　controller.　The　principle　of　the　controller　is　elucidated　and　the　controlling　equations　of　adjusting　system　is　established.　Factors　that　influence　the　controlling　performances　are　analyzed　through　studying　of　experiments　and　theory,　which　provides　guidance　for　practical　operations　and　stabilizations　of　adjusting　system.　It　is　demonstrated　through　applications　that　the　controller　can　satisfy　actual　demand　of　industrial　production　process　under　50%　variations　of　work　conditions.　As　there　is　no　moving　parts,　the　controller　has　a　variety　of　advantages　such　as　non-leaking,　high　safety　credibility,　strong　adjusting　capability,　low　coast,　high　economical　efficiency　and　broad　application　expectations　in　steam-liquid　systems　where　liquid　level　needs　to　maintain.